How do my outdoor plants survive the winter?

peterboroughmastergardeners

April 1

By Mary-Jane Pilgrim, Master Gardener

Have you ever wondered how some plants manage to survive freezing temperatures while others wither away at the slightest frost? It all comes down to a fascinating trait called hardiness.

Hardiness in plants refers to their ability to endure cold weather conditions, especially freezing temperatures, without being damaged. Plants that are considered hardy have evolved various mechanisms to protect themselves from the harsh effects of cold.

Most perennials sold in garden centres in our region are hardy if their tags refer to zone 5 or lower. Zone 6 perennials may survive if planted near a foundation in a sheltered spot. Trees are also labelled with a zone, and I've given up buying trees that are not in zone 4 or lower. Plants listed as "annuals" like most vegetable seedlings are simply not hardy at all in our zone. They may be hardy in other zones like Florida, though! In general, Peterborough is listed as hardiness zone 5a. The lower the number and letter of the alphabet, the colder it gets in the winter and the more hardy a plant needs to be in order to survive.

So how does hardiness work? One key factor contributing to a plant's hardiness is its genetic makeup. Some plants naturally possess traits that make them more resistant to freezing temperatures. These traits can include thickened cell walls which provide structural support and help prevent cell damage when temperatures drop. Additionally, certain plants produce antifreeze proteins that lower the freezing point of their cell fluids, allowing them to survive in sub-zero temperatures.

Another important aspect of plant hardiness is acclimation. Just like animals, plants can adapt to their environment over time. As temperatures gradually decrease in the fall, hardy plants undergo physiological changes that prepare them for the cold ahead. This process, known as cold acclimation, involves the production of protective compounds such as sugars and proteins, as well as changes in cell membrane composition to maintain fluidity and prevent cells from rupturing.

Lastly, some hardy plants have developed mechanisms to avoid freezing altogether. They might shed their leaves, which are more susceptible to damage, or enter a state of dormancy until warmer temperatures return.

In summary, a combination of genetic traits and adaptive mechanisms allows the hardy plants in my gardens and yours to brave some of the chilliest of climates.

Nature is simply amazing.